MazdaBoi

Hello,

I own a 94 FD, and recently began experiencing some drivetrain vibration. Wanted to get a little advice, if possible.

Just a little background. Engine is mildly modified. Larger injectors, fuel system has been upgraded, Power FC, turbos configured for non-sequential operation, boost controller, etc. Engine was rebuilt a year ago.

I'm not very hard on my baby. Weekend car. No racing or drag strips. Just some spirited driving here and there.

A couple weekends ago, was out driving on a windy road, and started to feel a vibration. Was bad enough that I pulled over, thinking I might have a tire that was going flat. Tires were fine. Lugnuts fine. Speed was about 65 or so.

Got back on the road, hit the interstate, and started working my way back home. Everything was fine for about 10 miles, then felt the vibration again. Was going up a moderate hill, about 75 mph. Let off the gas, drove slower the last couple miles and got off the exit. Didn't feel the vibration again.

Once home, I jacked the car up, tried to check for play in the driveshaft U-joints by spinning the wheels by hand. Didn't notice any significant slop.

Changed differential oil, just in case. Checked the drain plug for any metal filings. None found. Checked oil for filings. None found there either. The oil was in need of a change though.

Was out driving around tonight again, on the same path as before. Got on the interstate, and again noticed the vibration around the same speed and load. Pushed in clutch, vibration continued. Shifted into neutral, coasted, and it continued. Again, drove slow the rest of the way to the exit, and got home and parked.

Seems to only happen at higher speeds, continues whether in gear or out. Seems to stop once I come to a stop and start moving again.

Any ideas?

Thanks.

fendamonky

iTrader: (6)

Does it only start around 55 mph? If so, it may be poorly balanced tires..

adam c

iTrader: (2)

Thats what I would check first. Maybe one of your wheel balancing weights fell off.

MazdaBoi

Yes, the lowest speed this has happened was around 55 or so. Its intermittent, and only occurs at cruising speeds when it does occur. I suppose its possible that I threw a weight off a wheel or something, but I'd think it would happen consistently then. Guess that's cheap to rule out though...

I keep wondering about the driveshaft U-joints, but visual inspection didn't show anything obvious. Looked for play by rotating the tires by hand too, and again not much play. I suppose the only real way to tell would be to pull the shaft and measure everything.

Just kind of wanted to see what others thought before I started throwing parts at it.

Thanks.

96fd3s

+1, get your wheels balanced

imitek

Try the ballancing first
I've got a prop vibration on evo 4 at moment ever so slight moment in joint when u twist back and faward u can feel it
It did feel like a wheel ballancing issue at first but obviously they checked out fine

Any way u can get in on ramp try to simulate the same problem with some one under car

MazdaBoi

I'll give it a shot and get my wheels balanced this week.

Thank you all for the advice! I'll post back once done.